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The UPC requires that hot water at public lavatories must be at least 100°F. This ensures adequate sanitation while reducing scalding risks. Maximum limits (typically 110°F–120°F) are enforced with mixing valves to protect users. Correct answer: A. 100°F.

The UPC specifies that the minimum drain size for a water closet is 3 inches. Smaller sizes cannot handle the discharge volume and velocity. Larger sizes (4 inches) are required for additional fixtures or higher DFU loads. Correct answer: B. 3 inches.

The UPC requires that if a roof is used for human occupancy, vent terminals must extend at least 7 feet above the roof surface. This prevents sewer gases from being released at breathing level. Correct answer: B. 7 feet.

Using UPC gas piping capacity tables, a 1/2-inch pipe at 70 feet delivers only about 45,000 BTU/hr, while a 3/4-inch delivers around 96,000 BTU/hr—both insufficient. A 1-inch line, however, can deliver up to 190,000 BTU/hr at that distance, meeting the 150,000 BTU/hr demand. Oversizing to 1-1/4 inch would be unnecessary unless additional appliances are expected. Correct sizing ensures safety, efficiency, and proper combustion. Correct answer: C. 1 inch.

The Uniform Plumbing Code mandates that every potable water outlet discharging into a fixture must maintain an air gap separation to prevent cross-connection and contamination. The required air gap is at least twice the effective opening (outlet) diameter, but never less than 1 inch. For example, if the outlet is ½ inch in diameter, the air gap must be at least 1 inch (since twice the diameter is only 1 inch). The rationale is to provide a physical separation between potable supply and potential wastewater, preventing backflow or siphonage during negative pressure conditions. The rule protects public health by safeguarding potable water systems against contamination. Therefore, the correct answer is C. Three times the diameter of the outlet is too much, while UPC specifically enforces "twice the diameter but not less than 1 inch," which aligns with option C in principle.